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Herbal Medicine                                            
Cranberry (Vaccinium macrocarpon)   

Be aware that the U. S. Food and Drug Administration does not strictly regulate herbs and dietary supplements. There is no guarantee of strength, purity or safety of products containing or claiming to contain valerian. Decisions to use herbs or supplements should be carefully considered. Individuals using prescription drugs should discuss taking herbs or supplements with their pharmacists or health care providers before starting.


Scientists have studied cranberry for the following health problems:

Urinary tract infection prevention
Multiple studies report that taking cranberry juice or pills by mouth may help prevent urinary tract infections and may particularly work against the bacteria Escherichia coli. Side effects are common in human trials. A recent meta-analysis concludes that there is some evidence from two good-quality randomized clinical trials that cranberry juice may decrease the number of symptomatic urinary tract infections over a 12-month period in women. If it is effective for other groups such as children and elderly men and women is not clear. The large number of dropouts/withdrawals from some of the trials indicates that cranberry juice may not be acceptable over long periods of time. In addition, it is not clear what is the optimum dosage or method of administration (for example, juice or tablets). Further properly designed trials with relevant outcomes are needed.
Urinary tract infection treatment
Studies have found that cranberry is not helpful for treating urinary tract infections once they have already started. It may be used as an adjunct to conventional therapy. With the emergence of antibiotic resistant organisms, alternative antibiotic treatment is being sought out. Cranberry is a phytomedicine that has been proven effective for urinary tract infections and may prove as a promising alternative.
Cranberry has been studied for several other purposes, but without enough scientific evidence to make any recommendations. These areas of study include prevention of Helicobacter pylori infections (which may occur in the stomach or early part of the intestine and may cause ulcers), viral or fungal infections, kidney stones, dental plaque, cancer, urine acidification, care of urostomy sites and reduction of odor from urinary incontinence.

Early research suggests cranberry juice is not an effective treatment in the prevention of urinary tract infections caused by neurogenic bladder or in the treatment of urinary symptoms from prostate cancer radiation therapy.

Unproven Uses     

Cranberry has been suggested for many other uses, based on tradition or on scientific theories. However, these uses have not been thoroughly studied in humans, and there is limited scientific evidence about safety or effectiveness. Some of these suggested uses are for conditions that are potentially serious and even life-threatening. You should consult a health care provider before using cranberry for any unproven use.

Antifungal, Candida albicans
Bladder conditions
Bladder infections
Blood disorders
Chronic urinary tract infections
Decontamination of meats
Gallbladder disease
Improved brain function
Liver disorders
Prostate cancer
Recurrent cystitis
Rheumatoid arthritis
Stomach ailments
Vitamin B-12 absorption
Wound care

Potential Dangers     


Side Effects

Pregnancy And Breast-Feeding


Interactions with drugs, supplements and other herbs have not been thoroughly studied. The interactions listed below have been reported in scientific publications. If you are taking prescription drugs, speak with your health care provider or pharmacist before using herbs or dietary supplements.

Interactions With Drugs

Interactions With Herbs And Dietary Supplements


The doses listed below are based on scientific research, publications or traditional use. Because most herbs and supplements have not been thoroughly studied or monitored, safety and effectiveness may not have been proven. Brands may be made differently, with variable ingredients even within the same brand. Combination products often contain small amounts of each ingredient and may not be effective. Appropriate dosing should be discussed with a health care provider before starting therapy; always read the recommendations on a product's label. The dosing for unproven uses should be approached cautiously, because scientific information is limited in these areas.

For Urinary Tract Infection Prevention  Adults (Aged 18 Or Older)

Children (Younger Than 18):  The dosing and safety of cranberry have not been studied thoroughly in children, and it is recommended that you discuss doses with your child's health care provider before starting therapy. The amount of cranberry usually found in foods is often assumed to be safe. One study used doses of 300 milliliters of cranberry juice daily for three months in children aged 2 to 18 years; however, there is not enough scientific support or safety data for this dosage.


Although cranberry has been suggested for many conditions, the best evidence supports its use for preventing urinary tract infections. Cranberry has not been proven effective for any other health conditions. People taking proton-pump inhibitors, antacids, antibiotics and drugs removed from the body by the kidneys should consult their health care provider before taking cranberry in amounts greater than usually found in foods. People with diabetes should be aware that cranberry juice may be high in sugar; sugar-free cranberry juice products are available. Remember that tinctures may contain large amounts of alcohol and may cause nausea and vomiting if taken with the drug disulfiram or metronidazole. Consult your health care provider if you experience side effects.

The information in this monograph was prepared by the professional staff at Natural Standard, based on thorough systematic review of scientific evidence. The material was reviewed by the Faculty of the Harvard Medical School with final editing approved by Natural Standard.


  1. Natural Standard: An organization that produces scientifically based reviews of complementary and alternative medicine (CAM) topics
  2. National Center for Complementary and Alternative Medicine (NCCAM): A division of the U.S. Department of Health & Human Services dedicated to research

Selected Scientific Studies: Cranberry

Some of the more recent studies are listed below:

  1. Burger O, Ofek I, Tabak M, et al. A high molecular mass constituent of cranberry juice inhibits helicobacter pylori adhesion to human gastric mucus. FEMS Immunol Med Microbiol 2000;29(4):295-301.
  2. Campbell G, Pickles T, D'yachkova Y. A randomised trial of cranberry versus apple juice in the management of urinary symptoms during external beam radiation therapy for prostate cancer. Clin Oncol (R Coll Radiol) 2003;Sep, 15(6):322-328.
  3. Carson CF, Riley TV. Non-antibiotic therapies for infectious diseases. Commun Dis Intell 2003;27(Suppl):S143-S146.
  4. Cavanagh HM, Hipwell M, Wilkinson JM. Antibacterial activity of berry fruits used for culinary purposes. J Med Food 2003;Spring, 6(1):57-61.
  5. Chambers BK, Camire ME. Can cranberry supplementation benefit adults with type 2 diabetes? Diabetes Care 2003;Sep, 26(9):2695-2696.
  6. Dignam R, Ahmed M, Denman S, et al. The effect of cranberry juice on UTI rates in a long term care facility. The Journal of the American Geriatrics Society 1997;45(9):S53.
  7. Ebringer A, Rashid T, Wilson C. Rheumatoid arthritis: proposal for the use of anti-microbial therapy in early cases. Scand J Rheumatol 2003;32(1):2-11. Review.
  8. Grant P. Warfarin and cranberry juice: an interaction? J Heart Valve Dis 2004;Jan, 13(1):25-26.
  9. Greenberg JA, Newman SJ, Morgan MA. Cranberries and urinary-tract health: a knowledge assessment of American College of Obstetricians and Gynecologists fellows. J Altern Complement Med 2004;Aug, 10(4):603-605.
  10. Jepson RG, Mihaljevic L, Craig J. Cranberries for preventing urinary tract infections. Cochrane Database Syst Rev 2000;(2):CD001321.
  11. Kontiokari T, Sundqvist K, Nuutinen M, et al. Randomised trial of cranberry-lingonberry juice and Lactobacillus GG drink for the prevention of urinary tract infections in women. BMJ 2001;322(7302):1571-1573.
  12. Lee YL, Owens J, Thrupp L, et al. Does cranberry juice have antibacterial activity? JAMA 2000;283(13):1691.
  13. Linsenmeyer TA, Harrison B, Oakley A, et al. Evaluation of cranberry supplement for reduction of urinary tract infections in individuals with neurogenic bladders secondary to spinal cord injury: a prospective, double-blinded, placebo-controlled, crossover study. J Spinal Cord Med 2004;27(1):29-34.
  14. Lynch DM. Cranberry for prevention of urinary tract infections. Am Fam Physician 2004;Dec 1, 70(11):2175-2177. Review.
  15. McHarg T, Rodgers A, Charlton K. Influence of cranberry juice on the urinary risk factors for calcium oxalate kidney stone formation. BJU Int 2003;Nov, 92(7):765-768.
  16. Patel DA, Gillespie B, Sobel JD, et al. Risk factors for recurrent vulvovaginal candidiasis in women receiving maintenance antifungal therapy: results of a prospective cohort study. Am J Obstet Gynecol 2004;Mar, 190(3):644-653.
  17. Pedersen CB, Kyle J, Jenkinson AM, et al. Effects of blueberry and cranberry juice consumption on the plasma antioxidant capacity of healthy female volunteers. Eur J Clin Nutr 2000;54(5):405-408.
  18. Schlager TA, Anderson S, Trudell J, et al. Effect of cranberry juice on bacteriuria in children with neurogenic bladder receiving intermittent catheterization. J Pediatr 1999;135(6):698-702.
  19. Terris MK, Issa MM, Tacker JR. Dietary supplementation with cranberry concentrate tablets may increase the risk of nephrolithiasis. Urology 2001;57(1):26-29.
  20. Waites KB, Canupp KC, Armstrong S, DeVivo MJ. Effect of cranberry extract on bacteriuria and pyuria in persons with neurogenic bladder secondary to spinal cord injury. J Spinal Cord Med 2004;27(1):35-40.
  21. Wechsler A. Recurrent cystitis in non-pregnant women. Clin Evid 2003;Dec(10):2210-2218. Review. available.

Last updated June 02, 2005